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Volume 273 - 16th International Conference on B-Physics at Frontier Machines (BEAUTY2016) - Charm physics
Charm CPV and rare decays at LHCb
M.J. Morello
Full text: pdf
Published on: 2016 November 15
Charm physics has been playing all along a role in particle physics, by contributing to the formulation of the
Standard Model (SM) as it is known nowadays.
The level of attention on it has tremendously increased in recent years because of the first experimental observations
of the slow mixing rate of the $D^0-\overline{D}^0$ flavour oscillations, providing definitely a full range of probes, entirely complementary
to the $B$ and $K$ mesons, for mixing and CP violation. In fact the charm quark is the only up-type quark that manifests flavour oscillations.
Only in recent years it has been possible to collect huge and very clean
samples of $D$ meson decays, several orders of magnitude larger in size than in the past, allowing also for the first time approaching
the small SM expectations for CP-violation below the $10^{-3}$ level.
Thus, the dynamics of the charm quark can be
probed for the presence of New Physics with negligible SM ``background'', since
any generic non-SM contribution would naturally carry additional CP-violating phases, which could enhance the observable
CP-violation relative to SM predictions. It is worth to mention that $D^0-\overline{D}^0$ mixing can proceed
in the SM through a double weak boson exchange (short distance contributions) or through intermediate states that are accessible to both $D^0$ and
$\overline{D}^0$ (long distance contributions).
The potentially large long distance contributions are non--perturbative and therefore difficult to estimate from the theory, however the interplay of many and even more precise experimental measurements, that only recently approached the desired precision,
along with the foreseen theoretical improvements in calculating such amplitudes, should allow constraining theoretical uncertainties in the next and far
future increasing the sensitivity to possible contributions from new processes
and particles at mass scales beyond the reach of direct searches.

The LHCb experiment at the Large Hadron Collider is currently the main player and this brief write-up covers the most recent LHCb results on CP-violation in the charm sector and on the search of rare charm decays.
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